Fiberglass Pool Prevention
- Thread starter jwgillis
- Start date
- Jul 21, 2013
- 53,587
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
What type of stains are you looking to prevent?
Don't put iron or copper in your pool water to prevent the common staining.
The stains may be cobalt as well, the "black plague." There are treatments and products just for that.
Stain is a light grey ring around the pool where side of pool meets floor of pool. Only on side that gets the most shade. Drain and acid wash required to remove.
- Jun 22, 2014
- 48,028
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
sktn77a
Gold Supporter
Decision by me. Acid wash by the Pool company that takes care of my pool. Owner did it. Been with company 11 years. Pool was drained for Kool Deck installation. Stain observed. Took advantage of pool drain and had it acid washed. Acid washed one time before (2017) because of small stain as I was to lazy to go through other stain removal process. Pool is 17 years old. Agree "typically don't acid wash fiberglass pools" but don't know of any reason not to do it if need arises.
I'm just looking for an additive that will help prevent staining of a Fiberglass pool ... if one exists.
I'm just looking for an additive that will help prevent staining of a Fiberglass pool ... if one exists.
- Jul 21, 2013
- 53,587
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
If it was only on the shady side, it’s likely the stain maybe algae and more chlorine may take care of that. What is your average chlorine and CYA levels?
Last edited:
Chlorine 5-7 / CYA - 60-70
Live in Yuma, AZ - Sunniest place in USA ... not hottest ... just more days of sun. Result is need for higher CYA ... initially raise to 90 and add when drops to 60.
Discounted algae due to light grey color and no stain on side of the pool that gets the most sun.
Live in Yuma, AZ - Sunniest place in USA ... not hottest ... just more days of sun. Result is need for higher CYA ... initially raise to 90 and add when drops to 60.
Discounted algae due to light grey color and no stain on side of the pool that gets the most sun.
- Jun 22, 2014
- 48,028
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
I'm familiar with Yuma from my days at Luke AFB. Know it well. I initially suspected the discoloration may be attributable to UV penetration on that side where the afternoon sun becomes the most intense, that coupled wither the aging gelcoat. That's one theory, but then I wouldn't expect an acid wash to help. But if you did this in the past and an acid wash did improve the issue, one would think the discoloration may be more calcium related. I'm sure hard water is an issue in your area, however why it would be more prevalent on just one side or near the bottom is a bit odd. 
I'm going to tag @JoyfulNoise for his opinion. In the meantime, it doesn't look like anyone has requested a full set of test results, so if you could do that for us it might help in our analyses and replies.
I'm going to tag @JoyfulNoise for his opinion. In the meantime, it doesn't look like anyone has requested a full set of test results, so if you could do that for us it might help in our analyses and replies.
- May 23, 2015
- 24,503
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
If was a grey stain that was removed by applying acid then it was most likely "dirty" calcium/mineral scale. Calcium carbonate is white naturally but when it precipitates from water it will pick up any suspended solids and form an off-white to dark grey color. Being in Yuma, you are also in the "Winter Vegetable Capital of the World" which means lots of farms and tons of atmospheric dust. You also will have very hard water like anywhere else in Southern AZ. Also, many people in Arizona make the mistake of using calcium hypochlorite to chlorinate pools and will often "sprinkle" that around a pools edge as well as add liquid chlorine and other chlorinating granules (dichlor) by that method. Pool techs are not know to be mindful in how they add chemicals. So often a large amount of chlorine and, possibly calcium, winds up at the bottom edge of the pool. This can cause a spike in pH and calcium hardness leading to scale and staining. Your description sounds very much like that.
Your options are to either control your CH carefully by using softened water (my pool's autofill is hooked up to our whole house water softener) or to control CH by periodically draining and refilling your pool. If you are using chlorine in your pool, it should come primarily from liquid chlorine, not solid sources.
As for products to control scale, you can use any HEDP based phosphonate scale inhibitor but it's not a one-time deal. You will add a startup dose and then regular maintenance dosing to keep the scale preventer at the appropriate concentration. It will be an ongoing cost and several of the best scale preventers cost upwards of $40/gallon. You will be using gallons of the stuff every month. Scale inhibitors will cause your phosphate levels to rise. Phosphates are algae nutrients and so as the phosphate levels rise, so will the risk of algae and you will need to keep tight control of your FC/CYA ratio to ensure that you don't dip below the minimum. Otherwise, algae can get a foothold and then you'll be SLAM'ing a pool which is no easy task when the CYA is up near 90ppm.
Your options are to either control your CH carefully by using softened water (my pool's autofill is hooked up to our whole house water softener) or to control CH by periodically draining and refilling your pool. If you are using chlorine in your pool, it should come primarily from liquid chlorine, not solid sources.
As for products to control scale, you can use any HEDP based phosphonate scale inhibitor but it's not a one-time deal. You will add a startup dose and then regular maintenance dosing to keep the scale preventer at the appropriate concentration. It will be an ongoing cost and several of the best scale preventers cost upwards of $40/gallon. You will be using gallons of the stuff every month. Scale inhibitors will cause your phosphate levels to rise. Phosphates are algae nutrients and so as the phosphate levels rise, so will the risk of algae and you will need to keep tight control of your FC/CYA ratio to ensure that you don't dip below the minimum. Otherwise, algae can get a foothold and then you'll be SLAM'ing a pool which is no easy task when the CYA is up near 90ppm.
Last edited:
Texas Splash/JoyfulNoise ... Thanks, Great Help! I'm buying "dirty" calcium/mineral scale." Logic follows: Yuma notorious for hard water; Calicum level of water is so high that I stopped testing for calicum after my first attempt 17 years ago ... was going to empty calicum "drop test" bottle before even approaching an acceptable rereading; Acid wash did remove the "stain." I "drop test" (TF Test Kit - TF 100) every 90 days. Oct 2022 results follow: TA 60 / pH 7.5 / Total Chlorine 8.5 / Free Chlorine 8 / Combined Chlorine .5 / CYA 50 / Calicum-Not tested.
Also, "Addative to help prevent stain" not needed equals $$ saved!
Also, "Addative to help prevent stain" not needed equals $$ saved!
